Tungsten nickel alloy of high density



April 12, 1949. J. KURTZ TUNGSTEN NICKEL {ALLOY OF HIGH DENSITY Filed Aug. 30, 1945 INVENTOR Z4605 KU/PTZ Patented Apr. 12, 1949 UNITEDSTA'l'Efi A'EENT @EHCE TUNGSTEN NICKEL ALLOY OF HIGH DENSITY 3 Claims.

The present invention relates to a tungsten alloy which has a densityapproximating the theoretical density of pure hot swaged tungsten andwhich has greater machinability and workability than such pure tungsten.

It has been a matter of great interest to metallurgists to producetungsten alloys that have the desirable mechanical properties of puretungsten and greater machinability, but such alloys as have beenproduced are generally considerably below the theoretical density of thepure hot swaged tungsten and consequently lack the desirable mechanicalproperties.

It is the object of the present invention to produce an alloy mainly oftungsten having a density approximating that of pure hot swaged tungstenand having greater machinability and better mechanical properties thanpure tungsten.

Attempts have been made to form an alloy consisting of large grains oftungsten cemented together by copper or nickel. Such alloys, however,have not been of value for if copper alone is used no alloying takesplace between the tungsten and copper and the resulting product is not atrue alloy. The tungsten rains do not increase in size or shape butremain in their original condition, being merely cemented together in aporphyritic structure. Furthermore, the copper does not fill all theintergranular voids and the product is of low density and lacks thedesirable mechanical properties.

On the other hand, if nickel alone is used, a true alloying takes placebetween the nickel and tungsten grains. The alloy so formed,nevertheless, does not permeate the entire body but much of the nickelgathers in large pools, leaving many of the tungsten grains unalloyedand a large number of intergranular voids among these grains. Thisproduct is also of low density and deficient in mechanical properties.

It has, however, been proposed to form an alloy of tungsten with bothnickel and copper and this has been more successful since anickel-coppertungsten alloy is formed that fills substantially all theintergranular spaces between the tungsten grains. The alloy so formed,however, while much superior to that formed with copper alone or nickelalone, has a density of only slightly more than 16 grams per c. c.'ascompared with the theoretical density of pure hot swaged tungsten of19.3 grams per 0. c. and is still somewhat lacking in the desirablemechanical properties. The structure shows very large grains, therebeing less than 1500 grains per square millimeter.

I have discovered that by the addition Of very small percentages ofplatinum, platinum family metals, or gold, to an alloy of tungsten andnickel without any copper, a very remarkable increase in density can beattained, The platinum family metals here referred to are palladium,iridium, osmium, ruthenium and rhodium. This is a very remarkablephenomenon in view of the fact that the amount of such added metals neednot be more than 0.1 per cent. and should be within the range of 0.05and 1.0%. Larger amounts produce no greater benefit and merely add tothe cost. In his Patent No. 2,183,359, Smithells discloses that an alloyof 95% tungsten and 5% nickel has a density of less than 14. Applicanthas found that by replacing 0.1% tungsten by 0.1% of platinum, therebyforming an alloy consisting of 94.9% tungsten, 5% nickel and 0.1% ofplatinum, he can obtain an alloy having a density of 18.3.

According to the method of the present invention, purified tungstenpowder having a particle size of from 1 to 25 microns is thoroughlymixed with nickel in proportion of from -95% tung sten, to 515% nickel,and platinum to an amount of from 0.05 to 1.0% is added.

The platinum is preferably added in the form of an aqueous solution ofchlor-platinic acid to the mixture of the tungsten-nickel powders. Thismixture, after the platinum addition, is dried with constant stirring toassure a uniform distribution of the platinum in the dried mixture ofpowders. The mixture is then placed in a suitable container and then putthrough a furnace under hydrogen atmosphere to remove any traces ofoxidation that might have taken place during the platinum addition. Thereduced powders are then sieved, ballmilled, pressed into ingot form andsintered at a temperature of about 1500 C. for about one hour. Likewise,other water soluble salts of the platinum group metals can be added inthe same amounts as specified for platinum. These metals includepalladium, iridium, rhodium, osmium and ruthenium. Gold also may be usedin the same amounts.

The resulting body shows a very considerable increase in grain size anda marked alloying of the tungsten and nickel evidenced by the roundedform of the grains. In the drawings, Fig. 1 shows a structure resultingfrom an alloy containing 94.9% tungsten, 5% nickel and-0.1% platinum;Fig. 2 shows the structure obtained with tungsten, 5% nickel and noplatinum. It will be observable that, in Fig. 1 the grain structure hasbeen greatly modified from the original sharp angular condition of thegrains before sintering. In Fig. 2 the grain structure is hardlymodified at all and the grains are small, sharp and angular. The graincount of Fig. 1 shows about 2500 grains to the square millimeter andthere are only very small pools of nickel observable, while in Fig. 2very large pools of nickel are present. Intergranuler voids are almostentirely absent in Fig. 1, while in Fig. 2 voids are observable inconsiderable number amongst the grains. In both drawings the indicatingnumeral 1 indicates the tungsten alloy grains, 2 "indicates the nickelpools, vand .3 the intergranular voids.

The invention will be more clearly understood-a from the drawings inwhich Fig. 1 is .a representation of a"sample"ofthe.i

alloy of the invention containing 94.9% tungsten, 5% nickel and 0.1platinum;

Fig. 2 is an alloy not of the invention containing 95% tungsten, 5%nickel andno platinum;

Fig. 3 is an alloy of the invention containing;

89.9% tungsten, 10% nickel and again 0.1% platinum; and

Fig.4}: isLan alloy. not of the invention but corresponding to.Fig.3,..containing 90% tungsten and 10%. nickel, ivith'no platinum.

The figures are :enlarged by. 300 diameters.

The. alloy, shown in Fig. 1 has a density of 18.3, although itscomposition diifers from the 95% tungsten 5%. nickelalloy of Smithells(which has a density ch14) only in the fact that there is 0.1

of .platinunradded. The grain count is much 17.3, agrain-countrof. 3000to the square millimeten and azhardnesson the RockwellA scale of 66,whileuonthe other hand the alloy of Fig. 4, with 90% tungsten and 10%nickeLwithout any platinum,-shows -a structure very-similar to that ofFig; 2,.:the-.grains=.being sharp andvnot. much a1 teredfi'from theiroriginalncondition. Large pools a of rnickel are also-observedthroughout. The structures shown in Figs..-1 and 3 have goodmachinability despitewtheir highdensity andhardi HESS.

The density of these alloys can be materially increased withoutnoticeable loss of mechanical properties by enlarging the time duringwhich the sintering takes place. The structures shown in Figs. 1 to 4were sintered at about 1500 C. for a period of about one hour, and ifthis period is extended to five hours or somewhat more, there will be anincrease in grain size and somewhat fewer pools of nickel.

The "illustrations above'given are specific to platinum as the addedmetal. However, if 0.1% of gold or of any of the other platinum familymetals mentionedabove are substituted for platinum, the results will beapproximately the same. The amount of these added metals is so smallthatit is desirable to add them as solutions of Water soluble compoundsso that they may be evenly distributed throughout the tungsten andnickel powders by stirring, after which they are reduced to metal.Aqueous solutions of chlorplatinic acid, gold chloride, palladiumchloride, etc:; may. be: used.

Having thus describedmy invention, what I claimis:

l. Tungsten nickel alloyxhaving. a density of ZrTungsten nickel alloy ofhigh density and goiodcmachinability consisting of 84 to 94.95% oftungsten; 5 to 15% of nickel and 0.05 to 1.0% of platinum, and having adensity of more than 17 grams per: cubic centimeter.

3;Tungsten nickel alloy of high density and good machinabilityconsisting of 94.9% of tungsten,.5% of nickel and 0.1% of platinum andhaving a density of 18.3 grams per cubic centimeter.

JACOB KURTZ.

REFERENCES CITED Theioll'owingreferences are of record in the file ofthis patent? UNITED STATES PATENTS Number Name 1 Date 2,072,368 Jedele-1 Mar. 2, 1937 2,167,240 Hensel July 25, 1939 2,183,359 Smithells Dec.12, 1939 2,227,446 Driggs Jan. 7, 1941

